Global cognition and 8-year survival among Japanese community-dwelling older adults

We sought to examine the longitudinal relationship between cognitive function and all-cause mortality among Japanese community-dwelling older adults, using an 8-year prospective cohort study design with mortality surveillance.

A total of 454 men and 386 women, aged 70 years and older, participated in the study. The Mini Mental State Examination (MMSE) was administered to assess global cognition. The total MMSE score and subscale scores were used as independent variables, and age, gender, education level, chronic disease, sensory deficit, depressive symptoms, and instrumental activities of daily living were used as covariates.

During the follow-up period, 191 subjects (139 men and 52 women) died, and 64 subjects (31 men and 33 women) moved to a different region of Japan and were lost to follow-up. Use of the multivariate Cox proportional hazards model, adjusted for potential confounders, showed that global cognition was significantly and independently associated with mortality (hazard ratio [HR] = 1.59, 95% confidence interval [CI]: 1.14-2.23 and HR = 2.81, 95% CI: 1.77-4.36 for the middle [24-27 points] and lowest [0-23 points] categories, respectively). Among the MMSE subscales, place orientation (HR = 1.57, 95% CI: 1.09-2.25), calculation (HR = 1.67, 95% CI: 1.18-2.35), and delayed recall (HR = 1.42, 95% CI: 1.03-1.96), were also significantly and independently associated with mortality.

Our study suggests that among older individuals, those with lower levels of cognitive function are more likely to have a shorter lifespan compared with those with higher cognitive functioning.